// Copyright 2018 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

"use strict";

(() => {
    const enosys = () => {
        const err = new Error("not implemented")
        err.code = "ENOSYS"
        return err
    }

    if (!globalThis.fs) {
        let outputBuf = ""
        globalThis.fs = {
            constants: { O_WRONLY: -1, O_RDWR: -1, O_CREAT: -1, O_TRUNC: -1, O_APPEND: -1, O_EXCL: -1 }, // unused
            writeSync(fd, buf) {
                outputBuf += decoder.decode(buf)
                const nl = outputBuf.lastIndexOf("\n")
                if (nl !== -1) {
                    console.log(outputBuf.substring(0, nl))
                    outputBuf = outputBuf.substring(nl + 1)
                }
                return buf.length
            },
            write(fd, buf, offset, length, position, callback) {
                if (offset !== 0 || length !== buf.length || position !== null) {
                    callback(enosys())
                    return
                }
                const n = this.writeSync(fd, buf)
                callback(null, n)
            },
            chmod(path, mode, callback) { callback(enosys()) },
            chown(path, uid, gid, callback) { callback(enosys()) },
            close(fd, callback) { callback(enosys()) },
            fchmod(fd, mode, callback) { callback(enosys()) },
            fchown(fd, uid, gid, callback) { callback(enosys()) },
            fstat(fd, callback) { callback(enosys()) },
            fsync(fd, callback) { callback(null) },
            ftruncate(fd, length, callback) { callback(enosys()) },
            lchown(path, uid, gid, callback) { callback(enosys()) },
            link(path, link, callback) { callback(enosys()) },
            lstat(path, callback) { callback(enosys()) },
            mkdir(path, perm, callback) { callback(enosys()) },
            open(path, flags, mode, callback) { callback(enosys()) },
            read(fd, buffer, offset, length, position, callback) { callback(enosys()) },
            readdir(path, callback) { callback(enosys()) },
            readlink(path, callback) { callback(enosys()) },
            rename(from, to, callback) { callback(enosys()) },
            rmdir(path, callback) { callback(enosys()) },
            stat(path, callback) { callback(enosys()) },
            symlink(path, link, callback) { callback(enosys()) },
            truncate(path, length, callback) { callback(enosys()) },
            unlink(path, callback) { callback(enosys()) },
            utimes(path, atime, mtime, callback) { callback(enosys()) },
        }
    }

    if (!globalThis.process) {
        globalThis.process = {
            getuid() { return -1 },
            getgid() { return -1 },
            geteuid() { return -1 },
            getegid() { return -1 },
            getgroups() { throw enosys() },
            pid: -1,
            ppid: -1,
            umask() { throw enosys() },
            cwd() { throw enosys() },
            chdir() { throw enosys() },
        }
    }

    if (!globalThis.crypto) {
        throw new Error("globalThis.crypto is not available, polyfill required (crypto.getRandomValues only)")
    }

    if (!globalThis.performance) {
        throw new Error("globalThis.performance is not available, polyfill required (performance.now only)")
    }

    if (!globalThis.TextEncoder) {
        throw new Error("globalThis.TextEncoder is not available, polyfill required")
    }

    if (!globalThis.TextDecoder) {
        throw new Error("globalThis.TextDecoder is not available, polyfill required")
    }

    const encoder = new TextEncoder()
    const decoder = new TextDecoder("utf-8")

    globalThis.Go = class {
        constructor() {
            this.argv = ["js"]
            this.env = {}
            this.exit = (code) => {
                if (code !== 0) {
                    console.warn("exit code:", code)
                }
            }
            this._exitPromise = new Promise((resolve) => {
                this._resolveExitPromise = resolve
            })
            this._pendingEvent = null
            this._scheduledTimeouts = new Map()
            this._nextCallbackTimeoutID = 1

            const setInt64 = (addr, v) => {
                this.mem.setUint32(addr + 0, v, true)
                this.mem.setUint32(addr + 4, Math.floor(v / 4294967296), true)
            }

            const setInt32 = (addr, v) => {
                this.mem.setUint32(addr + 0, v, true)
            }

            const getInt64 = (addr) => {
                const low = this.mem.getUint32(addr + 0, true)
                const high = this.mem.getInt32(addr + 4, true)
                return low + high * 4294967296
            }

            const loadValue = (addr) => {
                const f = this.mem.getFloat64(addr, true)
                if (f === 0) {
                    return undefined
                }
                if (!isNaN(f)) {
                    return f
                }

                const id = this.mem.getUint32(addr, true)
                return this._values[id]
            }

            const storeValue = (addr, v) => {
                const nanHead = 0x7FF80000

                if (typeof v === "number" && v !== 0) {
                    if (isNaN(v)) {
                        this.mem.setUint32(addr + 4, nanHead, true)
                        this.mem.setUint32(addr, 0, true)
                        return
                    }
                    this.mem.setFloat64(addr, v, true)
                    return
                }

                if (v === undefined) {
                    this.mem.setFloat64(addr, 0, true)
                    return
                }

                let id = this._ids.get(v)
                if (id === undefined) {
                    id = this._idPool.pop()
                    if (id === undefined) {
                        id = this._values.length
                    }
                    this._values[id] = v
                    this._goRefCounts[id] = 0
                    this._ids.set(v, id)
                }
                this._goRefCounts[id]++
                let typeFlag = 0
                switch (typeof v) {
                    case "object":
                        if (v !== null) {
                            typeFlag = 1
                        }
                        break
                    case "string":
                        typeFlag = 2
                        break
                    case "symbol":
                        typeFlag = 3
                        break
                    case "function":
                        typeFlag = 4
                        break
                }
                this.mem.setUint32(addr + 4, nanHead | typeFlag, true)
                this.mem.setUint32(addr, id, true)
            }

            const loadSlice = (addr) => {
                const array = getInt64(addr + 0)
                const len = getInt64(addr + 8)
                return new Uint8Array(this._inst.exports.mem.buffer, array, len)
            }

            const loadSliceOfValues = (addr) => {
                const array = getInt64(addr + 0)
                const len = getInt64(addr + 8)
                const a = new Array(len)
                for (let i = 0; i < len; i++) {
                    a[i] = loadValue(array + i * 8)
                }
                return a
            }

            const loadString = (addr) => {
                const saddr = getInt64(addr + 0)
                const len = getInt64(addr + 8)
                return decoder.decode(new DataView(this._inst.exports.mem.buffer, saddr, len))
            }

            const timeOrigin = Date.now() - performance.now()
            this.importObject = {
                _gotest: {
                    add: (a, b) => a + b,
                },
                gojs: {
                    // Go's SP does not change as long as no Go code is running. Some operations (e.g. calls, getters and setters)
                    // may synchronously trigger a Go event handler. This makes Go code get executed in the middle of the imported
                    // function. A goroutine can switch to a new stack if the current stack is too small (see morestack function).
                    // This changes the SP, thus we have to update the SP used by the imported function.

                    // func wasmExit(code int32)
                    "runtime.wasmExit": (sp) => {
                        sp >>>= 0
                        const code = this.mem.getInt32(sp + 8, true)
                        this.exited = true
                        delete this._inst
                        delete this._values
                        delete this._goRefCounts
                        delete this._ids
                        delete this._idPool
                        this.exit(code)
                    },

                    // func wasmWrite(fd uintptr, p unsafe.Pointer, n int32)
                    "runtime.wasmWrite": (sp) => {
                        sp >>>= 0
                        const fd = getInt64(sp + 8)
                        const p = getInt64(sp + 16)
                        const n = this.mem.getInt32(sp + 24, true)
                        fs.writeSync(fd, new Uint8Array(this._inst.exports.mem.buffer, p, n))
                    },

                    // func resetMemoryDataView()
                    "runtime.resetMemoryDataView": (sp) => {
                        sp >>>= 0
                        this.mem = new DataView(this._inst.exports.mem.buffer)
                    },

                    // func nanotime1() int64
                    "runtime.nanotime1": (sp) => {
                        sp >>>= 0
                        setInt64(sp + 8, (timeOrigin + performance.now()) * 1000000)
                    },

                    // func walltime() (sec int64, nsec int32)
                    "runtime.walltime": (sp) => {
                        sp >>>= 0
                        const msec = (new Date()).getTime()
                        setInt64(sp + 8, msec / 1000)
                        this.mem.setInt32(sp + 16, (msec % 1000) * 1000000, true)
                    },

                    // func scheduleTimeoutEvent(delay int64) int32
                    "runtime.scheduleTimeoutEvent": (sp) => {
                        sp >>>= 0
                        const id = this._nextCallbackTimeoutID
                        this._nextCallbackTimeoutID++
                        this._scheduledTimeouts.set(id, setTimeout(
                            () => {
                                this._resume()
                                while (this._scheduledTimeouts.has(id)) {
                                    // for some reason Go failed to register the timeout event, log and try again
                                    // (temporary workaround for https://github.com/golang/go/issues/28975)
                                    console.warn("scheduleTimeoutEvent: missed timeout event")
                                    this._resume()
                                }
                            },
                            getInt64(sp + 8),
                        ))
                        this.mem.setInt32(sp + 16, id, true)
                    },

                    // func clearTimeoutEvent(id int32)
                    "runtime.clearTimeoutEvent": (sp) => {
                        sp >>>= 0
                        const id = this.mem.getInt32(sp + 8, true)
                        clearTimeout(this._scheduledTimeouts.get(id))
                        this._scheduledTimeouts.delete(id)
                    },

                    // func getRandomData(r []byte)
                    "runtime.getRandomData": (sp) => {
                        sp >>>= 0
                        crypto.getRandomValues(loadSlice(sp + 8))
                    },

                    // func finalizeRef(v ref)
                    "syscall/js.finalizeRef": (sp) => {
                        sp >>>= 0
                        const id = this.mem.getUint32(sp + 8, true)
                        this._goRefCounts[id]--
                        if (this._goRefCounts[id] === 0) {
                            const v = this._values[id]
                            this._values[id] = null
                            this._ids.delete(v)
                            this._idPool.push(id)
                        }
                    },

                    // func stringVal(value string) ref
                    "syscall/js.stringVal": (sp) => {
                        sp >>>= 0
                        storeValue(sp + 24, loadString(sp + 8))
                    },

                    // func valueGet(v ref, p string) ref
                    "syscall/js.valueGet": (sp) => {
                        sp >>>= 0
                        const result = Reflect.get(loadValue(sp + 8), loadString(sp + 16))
                        sp = this._inst.exports.getsp() >>> 0 // see comment above
                        storeValue(sp + 32, result)
                    },

                    // func valueSet(v ref, p string, x ref)
                    "syscall/js.valueSet": (sp) => {
                        sp >>>= 0
                        Reflect.set(loadValue(sp + 8), loadString(sp + 16), loadValue(sp + 32))
                    },

                    // func valueDelete(v ref, p string)
                    "syscall/js.valueDelete": (sp) => {
                        sp >>>= 0
                        Reflect.deleteProperty(loadValue(sp + 8), loadString(sp + 16))
                    },

                    // func valueIndex(v ref, i int) ref
                    "syscall/js.valueIndex": (sp) => {
                        sp >>>= 0
                        storeValue(sp + 24, Reflect.get(loadValue(sp + 8), getInt64(sp + 16)))
                    },

                    // valueSetIndex(v ref, i int, x ref)
                    "syscall/js.valueSetIndex": (sp) => {
                        sp >>>= 0
                        Reflect.set(loadValue(sp + 8), getInt64(sp + 16), loadValue(sp + 24))
                    },

                    // func valueCall(v ref, m string, args []ref) (ref, bool)
                    "syscall/js.valueCall": (sp) => {
                        sp >>>= 0
                        try {
                            const v = loadValue(sp + 8)
                            const m = Reflect.get(v, loadString(sp + 16))
                            const args = loadSliceOfValues(sp + 32)
                            const result = Reflect.apply(m, v, args)
                            sp = this._inst.exports.getsp() >>> 0 // see comment above
                            storeValue(sp + 56, result)
                            this.mem.setUint8(sp + 64, 1)
                        }
                        catch (err) {
                            sp = this._inst.exports.getsp() >>> 0 // see comment above
                            storeValue(sp + 56, err)
                            this.mem.setUint8(sp + 64, 0)
                        }
                    },

                    // func valueInvoke(v ref, args []ref) (ref, bool)
                    "syscall/js.valueInvoke": (sp) => {
                        sp >>>= 0
                        try {
                            const v = loadValue(sp + 8)
                            const args = loadSliceOfValues(sp + 16)
                            const result = Reflect.apply(v, undefined, args)
                            sp = this._inst.exports.getsp() >>> 0 // see comment above
                            storeValue(sp + 40, result)
                            this.mem.setUint8(sp + 48, 1)
                        }
                        catch (err) {
                            sp = this._inst.exports.getsp() >>> 0 // see comment above
                            storeValue(sp + 40, err)
                            this.mem.setUint8(sp + 48, 0)
                        }
                    },

                    // func valueNew(v ref, args []ref) (ref, bool)
                    "syscall/js.valueNew": (sp) => {
                        sp >>>= 0
                        try {
                            const v = loadValue(sp + 8)
                            const args = loadSliceOfValues(sp + 16)
                            const result = Reflect.construct(v, args)
                            sp = this._inst.exports.getsp() >>> 0 // see comment above
                            storeValue(sp + 40, result)
                            this.mem.setUint8(sp + 48, 1)
                        }
                        catch (err) {
                            sp = this._inst.exports.getsp() >>> 0 // see comment above
                            storeValue(sp + 40, err)
                            this.mem.setUint8(sp + 48, 0)
                        }
                    },

                    // func valueLength(v ref) int
                    "syscall/js.valueLength": (sp) => {
                        sp >>>= 0
                        setInt64(sp + 16, Number.parseInt(loadValue(sp + 8).length))
                    },

                    // valuePrepareString(v ref) (ref, int)
                    "syscall/js.valuePrepareString": (sp) => {
                        sp >>>= 0
                        const str = encoder.encode(String(loadValue(sp + 8)))
                        storeValue(sp + 16, str)
                        setInt64(sp + 24, str.length)
                    },

                    // valueLoadString(v ref, b []byte)
                    "syscall/js.valueLoadString": (sp) => {
                        sp >>>= 0
                        const str = loadValue(sp + 8)
                        loadSlice(sp + 16).set(str)
                    },

                    // func valueInstanceOf(v ref, t ref) bool
                    "syscall/js.valueInstanceOf": (sp) => {
                        sp >>>= 0
                        this.mem.setUint8(sp + 24, (loadValue(sp + 8) instanceof loadValue(sp + 16)) ? 1 : 0)
                    },

                    // func copyBytesToGo(dst []byte, src ref) (int, bool)
                    "syscall/js.copyBytesToGo": (sp) => {
                        sp >>>= 0
                        const dst = loadSlice(sp + 8)
                        const src = loadValue(sp + 32)
                        if (!(src instanceof Uint8Array || src instanceof Uint8ClampedArray)) {
                            this.mem.setUint8(sp + 48, 0)
                            return
                        }
                        const toCopy = src.subarray(0, dst.length)
                        dst.set(toCopy)
                        setInt64(sp + 40, toCopy.length)
                        this.mem.setUint8(sp + 48, 1)
                    },

                    // func copyBytesToJS(dst ref, src []byte) (int, bool)
                    "syscall/js.copyBytesToJS": (sp) => {
                        sp >>>= 0
                        const dst = loadValue(sp + 8)
                        const src = loadSlice(sp + 16)
                        if (!(dst instanceof Uint8Array || dst instanceof Uint8ClampedArray)) {
                            this.mem.setUint8(sp + 48, 0)
                            return
                        }
                        const toCopy = src.subarray(0, dst.length)
                        dst.set(toCopy)
                        setInt64(sp + 40, toCopy.length)
                        this.mem.setUint8(sp + 48, 1)
                    },

                    "debug": (value) => {
                        console.log(value)
                    },
                },
            }
        }

        async run(instance) {
            if (!(instance instanceof WebAssembly.Instance)) {
                throw new TypeError("Go.run: WebAssembly.Instance expected")
            }
            this._inst = instance
            this.mem = new DataView(this._inst.exports.mem.buffer)
            this._values = [ // JS values that Go currently has references to, indexed by reference id
                Number.NaN,
                0,
                null,
                true,
                false,
                globalThis,
                this,
            ]
            this._goRefCounts = Array.from({ length: this._values.length }).fill(Infinity) // number of references that Go has to a JS value, indexed by reference id
            this._ids = new Map([ // mapping from JS values to reference ids
                [0, 1],
                [null, 2],
                [true, 3],
                [false, 4],
                [globalThis, 5],
                [this, 6],
            ])
            this._idPool = [] // unused ids that have been garbage collected
            this.exited = false // whether the Go program has exited

            // Pass command line arguments and environment variables to WebAssembly by writing them to the linear memory.
            let offset = 4096

            const strPtr = (str) => {
                const ptr = offset
                const bytes = encoder.encode(`${str}\0`)
                new Uint8Array(this.mem.buffer, offset, bytes.length).set(bytes)
                offset += bytes.length
                if (offset % 8 !== 0) {
                    offset += 8 - (offset % 8)
                }
                return ptr
            }

            const argc = this.argv.length

            const argvPtrs = []
            this.argv.forEach((arg) => {
                argvPtrs.push(strPtr(arg))
            })
            argvPtrs.push(0)

            const keys = Object.keys(this.env).sort()
            keys.forEach((key) => {
                argvPtrs.push(strPtr(`${key}=${this.env[key]}`))
            })
            argvPtrs.push(0)

            const argv = offset
            argvPtrs.forEach((ptr) => {
                this.mem.setUint32(offset, ptr, true)
                this.mem.setUint32(offset + 4, 0, true)
                offset += 8
            })

            // The linker guarantees global data starts from at least wasmMinDataAddr.
            // Keep in sync with cmd/link/internal/ld/data.go:wasmMinDataAddr.
            const wasmMinDataAddr = 4096 + 8192
            if (offset >= wasmMinDataAddr) {
                throw new Error("total length of command line and environment variables exceeds limit")
            }

            this._inst.exports.run(argc, argv)
            if (this.exited) {
                this._resolveExitPromise()
            }
            await this._exitPromise
        }

        _resume() {
            if (this.exited) {
                throw new Error("Go program has already exited")
            }
            this._inst.exports.resume()
            if (this.exited) {
                this._resolveExitPromise()
            }
        }

        _makeFuncWrapper(id) {
            const go = this
            return function () {
                const event = { id, this: this, args: arguments }
                go._pendingEvent = event
                go._resume()
                return event.result
            }
        }
    }
})()
